1. Field of the Invention
The present invention relates to a helical structure and method and apparatus for manufacture thereof and, more particularly, to such an invention which permits helical structures to be manufactured in a form not heretofore achieved and having application in virtually all operative environments.
2. Description of the Prior Art
Helical structures, such as augers, screws, helical conveyors and the like, have application in a virtually limitless number of embodiments and operative environments. From antiquity, such structures have been employed for a vast assortment of purposes to achieve an equally impressive number of operational objectives. For example, the "Archimedean screw" was widely employed for moving water during the age of the Greeks. Essentially, such devices include a helical flight which is rotated about an axis of rotation to move material along a path of travel generally parallel to the axis of rotation.
In view of the antiquity of this basic mechanical movement, the prior art is replete with various embodiments of such helical structures as well as methods and apparatuses for the manufacture thereof. In general, such prior art efforts have been directed to the manufacture of such helical structures in relatively short subsections which, when assembled, are interconnected along the axis of rotation to form a helical structure of the length desired. While it has been recognized that it would be desirable to manufacture such helical structures as single, integral units, the technology has not been available to achieve this objective as a practical matter. Among the advantages to be achieved in the manufacture of helical structures as a single unit include strength, minimization of cost, weight reduction, overall structural integrity, reliability of operation and the like.
It has also been recognized as desirable to manufacture helical structures from thermal plastic materials so as significantly to reduce weight while achieving all of the aforementioned objectives. For example, the Lundell U.S. Pat. No. 4,976,341 discloses a segmented auger assembled from a plurality of auger segments made of inert material, such as polyethylene, for use in conveying abrasive and corrosive materials. In the case of the Lundell segmented auger, the segments are endwardly interconnected to complete the segmented auger. Another version of such a prior art device is revealed by the Lapeyre U.S. Pat. No. 4,852,719 which discloses a modular screw conveyor. Each module is molded of a suitable plastic material and has integrally formed therewith a cylindrical body. The modules are adapted to be endwardly interconnected to provide a screw conveyor of the desired length. While such prior art efforts are advances in the art and effective in achieving their stated objectives, the inability to form a helical structure in the desired length as a single, unitary entity has been a significant disadvantage for all of the reasons noted.
The specific operative environments in which such helical structures are employed present other reasons for desiring to produce helical structures in single, unitary forms. For example, it has been recognized that augers employed in vending machines would possess significant operative advantages if manufactured in this single unitary form. The augers are mounted in upright relation supporting vendable objects on the flight wall thereof. The collective weight of the vendables, the stresses induced by the upright attitude and other factors present operational difficulties where the auger is of segmented construction.
Therefore, it is an object of the present invention to provide a helical structure and method and apparatus for manufacture thereof which permit virtually any helical structure to be formed as a single, unitary structure in a single manufacturing process; which permit helical structures to be formed from thermal plastic material in precisely the length desired and without the need for assembly of the helical structure itself; which permit the complex geometry of such a helical structure to be achieved in a molding operation permitting the subsections of the mold to be removed from each other to free the helical structure without difficulty or damage to the helical structure; which have particular utility in the manufacture of such helical structures as augers employed in vending machines to dispense vendable objects dependably and inexpensively without the disadvantages heretofore associated therewith; and which are otherwise entirely effective in achieving their operational objectives.